1. Field of the Invention
The present invention relates to a scene characteristics detection type video encoding apparatus capable of minimizing the degradation of picture quality derived from a scene change (a point of scene change).
2. Description of the Related Art
One of such conventional apparatuses is a video encoding apparatus, such as an MPEG2 encoder, accompanied with a TM5 (Test Model 5) oriented virtual buffer controller. In the apparatus, when a difference occurs between the target amount and the generated amount of data to be encoded, it is fed back for controlling a quantization accuracy. This allows the quantizing process to be stably carried out with the allocation of bits to an input video signal to be encoded determined corresponding to the encoding difficulty of the input video signal which may be varied more or less.
However, when the input video signal has two consecutive images appearing less correlated to each other such as before and after the point of scene change, a different between the generated amount of data and the target amount of data may increase. The different between the generated amount of data and the target amount of data is fed back to a process of determining the quantization accuracy due to a large change in the virtual buffer occupancy, thus causing an abrupt picture quality degradation in the beginning of a scene.
It is an object of the present invention to provide a scene characteristics detection type video encoding apparatus which can eliminate the foregoing disadvantage of a prior art and minimize the degradation of picture quality derived from the point of scene change.
In order to achieve the object, the present invention is characterized in comprising a means for detecting the point of scene change in an input video signal and releasing a scene attribute data including at least a data of a position distanced from the point of scene change; a means for estimating the encoding difficulty of the input video signal; and a means for determining the amount of data to be encoded for the input video signal in response to the scene attribute data and the encoding difficulty, wherein the means for determining the amount of data to be encoded for the input video signal is arranged for allocating a more number of bits to the input video signal which is close to the point of scene change. This allows the degradation of picture quality derived from the point of scene change to be minimized.
As the second feature of the present invention, a filtering means for pre-processing an input video signal prior to the encoding is provided and its filtering characteristic is updated in response to the scene attribute data and the encoding difficulty data. Accordingly, when the input video signal includes the point of scene change and its encoding difficulty is high, the filtering characteristic of the filtering means is updated for effectively eliminating high frequency components of the input video signal. This allows a more number of bits to be allocated to low frequency components of the input video signal which largely affect the subjective picture quality, hence minimizing the degradation of the picture quality.